Study objectives are to evaluate and compare safety, tolerance, pharmacokinetics and preliminary activity for Nevirapine at various doses orally administered daily over 24 weeks in mildly to moderately symptomatic HIV infected children between 2 months and 18 years of age and to evaluate safety, tolerance, pharmacokinetics, and preliminary activity for Nevirapine at various doses in combination with ZDV for 24 weeks in mildly to modertely symptomatic HIV infected children 2 months to 18 years of age.